Blast fence



B. S. LYNN BLAST FENCE March 14, 1961 2 Sheets-Sheet 1 Filed June 24,1957 March 14, 1961 B. s. LYNN 2,974,910

BLAST FENCE Filed June 24, 1957 2 Sheets-Sheet 2 0 INI/EN roR. Z35er/7am ,Wan/ey Lynn United States, Parent" BLAST FENCE.

Bernard` Stanley Lynn, 19451 Black Road, Los Gatos, Calif.

Filed June 24, 1951, ser. No. 661,445

1z claims.. (ci. 244-114) This invention relates generally to blastfences for deilecting the blast from aircraft power units of the jettype.

Various structures, generally referred to as blast fences, have beenused for deilecting the blast from power units o f the jet type. Suchstructures are desirable at the ends of runways where takeoff runscommence, and along test areas where units are being tested or repaired,or along run-up areas. A typical prior Iart blast fence employs aplurality of vertically spaced horizontal louvers or, vanes whichintercept the blast and deflect it upwardly. Another prior type of fenceis in the form of a chute which deilects the blast upwardly from itsnormal hori- Zontal direction. Such fence constructions, in contrastwith the present invention, lack certain desirable features.Particularly they are relatively expensive to construct and install, and:after installation they are relatively unsightly. The overalll heightis usually excessive, thus blocking the view from the cockpit of theaircraft. Although they deflect the blast upwardly at an inclination tothe horizontal, they do not provide the degree of protection desired. Inareas behind the fence, the jet noise is relatively heavy and the` airquite turbulent.

It is the general object of the present invention to provide a blastfence construction which overcomes the difficulties pointed out above.

Another object of the invention is to provide a blast fence which isrelatively inexpensive and simple to construct and erect, and which whenerected occupies a minimum amount of space. Another object is to providea blast fencewhich alords more. complete protection for surroundingareas, ,incl'ujdlifngv particularly the area immediately behind thefence.`

Another object is to provide a fence construction which materiallyreduces the noise of the blast as received. in adjacent areas.

Another object is to provide a blast fence construction which can bemade in sections :or units, which. are simple to transport and toconnect together to form a fence of the desired length.

l Another object is to provide a fence construction which can be readilyand quickly installed where desired, and' which can be readily removed4and salvaged for reuse.

Another object is to provide a blast fence making usev offatnewprinciple, namely that of a vertical pneumatic curtain which providesgreater protection for adjacent areas.l Another -.object is to.. providea fence whichl is not subjecf'to excessive heating.Y Additional objectsand features of the inventiontwill appear from the following descriptionin which the preferred embodiments have-beenset forth in detail inconjiinctionwith-the accompanying drawing.

.Referringi tothe. drawing:

. fence of extended. length having end and transverse walls.

Figure 6 is a view similar to Figure 1 but showing a modication in whichmeans is provided for cooling the device. f

Figure 7 is a view like Figure 3 but showing a modication.

The blast fence illustrated in Figures 1 and 2 consists of a main body10 formed of sheet metal, and providing a blast deflecting surface. Asuitable frame 11 serves to support the body and can consist of verticalposts 12, cross-connected by the beam 13. Suit-able means such as bolts14 serve to attach the upper portion of the body to the beam 13, whilethe lower end mayv be attached to the anchoring bolts. 16, which areembedded in the anchoring block 17.

I prefer to form the body 1t) of sheet metal, and particularly sheetmetal that is formed toa continuous curvature and stiifened by ribs orcorrugations. V-In the particular construction illustrated in Figures land 2 the corrugations extend vertically, and the curvature is such thatas viewed in section, the body conforms substantially to the segment ofa cylinder. To facilitate manufacture,v transporting the device, and itserection, it is desirable to form the body of a plurality of sections,as illustrated in Figure 2, the various sections having over-l lappingmargins attached together by means of bolts or rivets 18. Whendismantled the sections may be nested.

In -addition -to the main body it is desirable to provide the end w-alls19. These walls can be shaped as shown in Figure 1', each with a curvededge attached to the body by suitable means such as bolts 21. The freeedge can be reinforced tas by means of stiifening angles 22.

Means is provided for protecting the lower or leading edge of thecorrugated sheet metal. Thus as shown in Figure 3, a sheet metal strip2.3 extends for the lengthfof the fence, and is'bent to cover the loweredge fofthe corrugated metal in the manner shown. This strip.- prefsents an inclined face to a blast directed toward the,V fenceg, andblocks leakage of blast through the spaces ybeneath the raised portionsof the corrugations.

A feature of my fence is the fact that the body-isl formed to deflect ablast. upwardly, and discharge it witha major vertical directioncomponent. Preferably the deilecting surfaces are so formed that inaddition to av major vertical direction component, at least a portion ofthe deflected blast has a minor direction component backwardly towardthe direction of the blast. In Figure l this is accomplished byextending the upper edge to a level above the horizontal axis a, towhich the body is formed. In practice it is convenient to form the bodyas a one-quarter segment of a cylinder, `and mount the body in themanner shown in Figure l, whereby the lower edge of the body is offsetrearwardly with respect to the.y axis a. v

Figure 4 schematically'illustrates an area 24 where one" may desire. totest or warm up jet power units,y or whe-re jet aircraft may be locatedimmediately prior-to* proceed-V4 ing along a runway. The blast uponstriking the fence'is progressively deflected upwardly to discharge fromthe upper edge of the deliecting surface with a majorvert'b cal'direction component.

As may be noted from this and other figures, the height of the upperedge of the deflecting surface is greater than the transverse or frontto back dimension.

With the construction illustrated in Figures 1 and 4, the indicatedangle between a line tangent to the upper edge of the deflectingsurface, and the vertical, is about 12. Therefore a minor horizontaldirection component is imparted to the discharging gases, and this minorcomponent is in a direction back toward the source of the blast. Inpractice this angle may range from about 6 to 20.

' As shown in Figure 7, the lower edge of the sheet metal body may betangential to the ground surface. Thus in this instance the body 10acorresponds to a slightly greater than one-quarter cylindrical segment,

whereby its lower edge is substantially directly below the axis a. Thisavoids the use of a recess for receiving the lower edge of thecorrugated sheet metal and the strip 23, and permits vertical mountingfor the bolts 16.

When the blast from a jet power unit is directed toward the fence, arelatively thin layer of high velocity gas is formed close to thatsurface of the area 24 which intersects the cone 25 of the blast (Figure4), and also close to the delecting surface of the fence. Anotherrelatively thicker layer of gas, moving at a relatively lower speed, ispresent over the high velocity moving layer. The high velocity layertends to discharge from the upper edge of the fence with a minorbackwardly directed component as previously described. However, theslower moving layer, because of its relatively greater thickness, tendsto spill over the upper edge of any deecting surface. With my invention,the high velocity relatively thin layer of gas which is discharged fromthe upper edge of my fense with a direction component backwardly towardthe source of the blast, forms a pneumatic curtain which extendsvertically from the fence, and which serves to effectively interceptslower moving gases which would otherwise find their way into the areato the rear of the fence to cause turbulence. Thus all of the gases ofthe blast are delivered upwardly with a major vertical directioncomponent, thus providing complete protection in regions behind thefence.

It will be evident from the foregoing that my fence has a new principleof operation which makes possible cer tain new and advantageous results.As previously mentioned, complete protection is alforded against thegases of the blast in regions behind the fence. If dust and stones arecaught up by the blast, they are delivered in a nearly verticaldirection from the fence, thus avoiding an otherwise hazardouscondition. When the fence is in operation there is a noticeable decreasein the noise level in adjacent areas, in contrast with prior art fences.This is attributed to the fact that the fence tends to effectivelyreflect sound waves upwardly, and in addition the high velocitypneumatic curtain `forms a zone which by virtue of sound absorption,sound reflection, or other acoustic effect, minimizes the intensity ofnoise from the blast in the area behind the fence.

The end walls 19 are desirable in that they prevent the discharge of aportion of the blast from the ends of the fence, thus causing all of theblast to be delivered upwardly. Without these end walls, it would benecessary to considerably extend the length of the fence for properprotection. The corrugated construction of the body aids in discharge ofthe high velocity layer in the desired direction to form a pneumaticcurtain, and in addition provides a simple structure of the requisitestrength. As previously described, such a body may be attached tothesupporting frame only along its upper edge portion, with the loweredge being anchored to a ground area.

Forming the body in a plurality of sections in the manner illustrated inFigure 2, facilitates manufacture and transportation. Such sections canbe readily nested for transport and quickly erected to form a -fence ofthe desired length.

When the fence is in use the strip 23 prevents the leakage of gases anddirt under the `raised portions of the corrugations.

The height of the fence is not excessive, and as suggested should not besuch as to block the view from the cockpit of the aircraft.

Since hot gases contact only one side of the sheet metal, the fence isnot subject to excessive heating in normal usage, in contrast withfences of the vane type where both sides of the vanes are exposed to hotgases.

As shown in Figure 5, where the fence is of considerable length, it isdesirable to use walls between the ends of the fence corresponding tothe end walls 19 of Figure l. Thus as shown in Figure 5, intermediatevertical walls 19a are mounted at regular intervals between the walls19, and serve to minimize lateral movement of the gases, thus causingthe gases of the blast to be delivered upwardly in the desired manner.

In some instances the blast may be of such intensity and temperature asto cause undue heating of the corrugated metal. For such conditions Ican employ the modication shown in Figure 6. Here a sprinkler pipe 26 ismounted adjacent the deflecting `strip 23, and is `connected to thewater supply pipe 27. By the operation of the solenoid valve 28, watercan be supplied to the sprinkler pipe 26 as desired, and the dischargingsprays of water caused to wet the surface of the body 10, thuspreventing excessive heating. Operation can be made automatic byproviding a suitable thermal responsive ele ment 29, mounted in heatconducted relation with the body, and connected by electrical circuitrywires 31 to operate the solenoid valve 28. With this arrangement whenthe temperature rises to a predetermined value,

water is automatically supplied to wet the surface of the body 10.

I claim:

l. In a blast fence adapted to be installed on a ground area to receiveand deect the blast from an aircraft power unit of the jet type, meansforming a substantially continuous and impervious blast dellectingsurface, said surface having at its bottom a horizontal leading edge andat its top an upper horizontal edge at a substantial elevation, saidsurface in vertical section being uniformly curved whereby a jet blastdirected against the surface is deflected upwardly for final dischargefrom the upper edge.

2. A blast fence as in claim 1 in which said surface is formed bysections of corrugated sheet metal with the corrugations in parallelvertical planes and all straight lines touching the surface from side toside are horizontal and therefore parallel to both edges of thedeflecting surface, whereby a jet blast directed toward the ysame is`edge with a major vertical direction component, said fence being closedat each end by a vertical plate to form an angularly disposed troughwith said plates limiting lateral movement of the gases of the jetblasts.

3. In a blast fence adapted to be installed on a ground area to receiveand deflect the blast from an aircraft power unit of the jet type, meansforming a substantially impervious blast deecting surface, said surfacehaving an upper horizontal edge at a substantial elevation, said surfacebeing smoothly curved to ybe concave as viewed from the source of theblast, the curvature of said surface being roughly a quarter of acylinder with its bottom edge parallel to the ground whereby a jet blastdirected against the surface is directed upwardly, and the transversehorizontal dimension of said surface being less than the height thereof.

- 4. In a blast fence adapted to receive the deect the blast from anaircraft power unit of the jettype, a corrugated sheet forming asubstantially impervious unbroken blast deecting surface, said surfacehaving au upper horizontal edge at a substantial elevation but below thelevel of the cockpit of the aircraft, said surface being continuouslycurved to conorrn roughly to the quarter segment of a cylinder having ahorizontal axis, whereby a jet blast directed toward the same isdeflected upwardly for final discharge from the upper edge.

5. A blast fence as in claim 4 in which the upper horizontal edge ofsaid surface is at an elevation above said horizontal axis, and thelower leading edge is parallel i to the upper edge and to the said aXisland is substantially directly beneath the latter, whereby a jet blastdirected toward the surface is deflected upwardly for final dischargefrom the upper edge with a major vertical direction component and aminor direction component of from to 20 backwardly toward the source ofthe blast.

6. The blast fence of claim 5 in which the minor component is roughhly12 and the deecting surface is supported in part by a frame secured tothe surface at a point below the upper edge and where the flow isvertical.

7. In a blast fence adapted to be installed on a ground area to receiveand deect the blast from an aircraft power unit of the jet type, aplurality of connected unbroken corrugated metal sheets forming asubstantially impervious blast deilecting surface, the surface of eachsheet having a lower leading edge parallel to the ground surface and anupper edge parallel thereto at an elevation just below the cockpit ofthe jet aircaft, said surface being arcuately concave as viewed from thesource of the blast and means for securing the connected sheets of thefence to the ground with the height of the upper edge greater than thetransverse horizontal dimension of the arcuate surface.

S. A blast fence to receive the blast from a jet aircraft power plantpositioned in front of the fence, comprising a frame secured to theground, a Substantially continuous and impervious blast deflecting bodyhaving a lower leading edge and an upper edge rearwardly thereof, meansfor securing the body to the ground proximate its leading bottom edge tosupport the lower portion of the body, and means for securing an upperportion of the body to said frame to support said upper portion; saidbody having a surface smoothly curved in vertical section substantiallytangent to a horizontal plane at its bottom leading edge andsubstantially tangent to a vertical plane at its upper portion wherebywhen said curved surface receives the top of the cone of the blast fromthe jet aircraft power plant at a level below the top of the body, theblast will be discharged upwardly from the top of the body, therebyprotecting the area of the ground behind the fence by reducing the jetnoise and minimizing turbulence there as the jet stream does not pass tothe rear of the fence.

9. A blast fence as in claim `8 together with vertically 6 disposedplates secured to said body at each end of the fence and verticalintermediate walls between the end plates serving to block ow of gaseslaterally, that is, in a direction endwise of the fence, whereby all ofthe blast will be discharged upwardly from the top edge of the fence.

10. The fence of claim 8 in which the frame comprises posts bolted tothe ground and a beam extending between the posts and bolted thereto;the leading bottom edge of the body is detachably secured to a verticalbolt anchored in the ground; the body is of corrugated sheet metal withthe ribs and valleys of the corrugations in vertical planes; the curvedsurface is a portion of a cylinder, the axis of which is in asubstantially vertical plane through the leading bottom edge of thebody, and in a horizontal plane at about the level of the beam; the bodyis of connected similar sections;y each end of the fence is closed by avertical plate; and intermediate walls parallel to the end platesprevent lateral movement of the gases of the jet blast.

1l. The fence of claim 8 in which the surface is approximately a quarterof a cylinder and the top of the fence is at a level below the cockpitof the usual airplane, whereby a relatively thin layer of the highvelocity blast gases strikes the bottom of the body so that the arcuatesurface defiects this high velocity layer to form a pneumatic curtainwhich intercepts the slower moving gases and causes all of the blast tobe delivered upward, thus avoiding the use of a higher fence.

l2. In a blast fence adapted to be installed on a ground area to receiveand dellect the blast from an aircraft power unit of the jet type, meansforming a substantially impervious blast deilecting surface, saidsurface having an upper discharge edge and a lower horizontal leadingedge, said surface being smoothly curved to be concave as viewed fromthe source of the blast, said means being of corrugated sheet metal withthe ribs and valleys of the corrugations in vertical planes, thecurvature of said surface being such that a jet blast directed againstthe surface is directed upwardly from the upper edge.

References Cited in the le of this patent UNITED STATES PATENTS1,026,806 Iblings May 21, 1912 1,866,008 Burke July 5, 1932 1,925,139Fellers Sept. 5, 1933 2,000,722 Steward May 7, 1935 2,608,363 ShumakerAug. 26, 1952 2,646,257 Krume July 21, 1953 2,720,276 Droeger Oct. 11,1955 2,726,830 Brown et al Dec. 13, 1955 2,826,382 Hayden Mar. 11, 1958

